It is known to control the pivoting motions of a loader shovel using parallelogram kinetics wherein the scoop-and-dump jack together with the operational truss, the loader chassis bearing the stationary link points and a drive lever displaceable along the operational truss form a parallelogram for at least one length of the jack. In order to enlarge the pivot-angle of the loader shovel, the drive lever is connected by a steering means with said shovel. For a particular parallelogram size, a loader shovel filled with dumping material retains its upward open pivoted position over the entire range of pivot motion of the operational truss. Even when the loader shovel is replaced by a stacking implement, the loaded material resting on the fork remains approximately parallel to its initial position over the entire pivoting path of the operational truss. The parallelogram kinetics entails the drawback that only the differential area of the jack piston will be hydraulically loaded when the loader shovel is retracted or when it is used to break out the material to be picked up. Moreover dumping is slower than retraction because the available oil flow must load all the jack cross-section when the loader shovel is being emptied by dumping.
On the other hand, as regards a so-called Z kinematics, the scoop-and-dump jack is connected at one end of the drive lever which in this case rests between its two ends and the loader shovel is connected by a control means to the other end. The rocker lever serves to so reverse the jack motions that to fill the loader shovel the entire piston area shall be available, but only the differential piston area will be for dumping. However this advantageous use of jack power also entails the drawback that the loader shovel or the fork of a forklift are not automatically kept parallel to the pivoting range of the operational truss and as a result the scoop-and-dump jack must be fine-controlled several times.